The coronavirus outbreak emerged in the Chinese city of Wuhan in late 2019 and was “extremely unlikely” to have been the result of a laboratory leak, according to a widely anticipated World Health Organization investigation into the origins of the pandemic.

In a version of the report circulated to WHO member states and seen by the Financial Times, scientists said the two most likely scenarios to explain the emergence of Covid-19 both involved the transmission of the virus from animals to humans. Estimates for when that occurred “ranged from late September to early December, but most estimates were between mid-November and early December”, it said.

Tedros Adhanom Ghebreyesus, WHO director-general, in a press conference on Monday, did not address questions on the findings directly. “For now all hypotheses will be on the table and will need further study,” he said.